#include "header.h"

// Table 14-6. Port C Pins Alternate Functions
// - PC0 -> ADC0 (ADC Input Channel 0)
//       -> PCINT8 (Pin Change Interrupt 8)
//
// 24.2 : The ADC generates a 10-bit result which is presented in the ADC Data Registers, ADCH and ADCL

#define INT_TO_HEX_CHAR(n) ((n) < 10 ? ('0' + (n)) : ('A' + ((n) - 10)))
void int_to_hex_string(uint64_t value, char *out, uint8_t num_digits) {
    for (uint8_t i = 0; i < num_digits; ++i) {
        uint8_t shift = (num_digits - 1 - i) * 4;
        out[i] = INT_TO_HEX_CHAR((value >> shift) & 0x0F);
    }
    out[num_digits] = '\0';
}
void word_to_hex(uint16_t value, char *out) {
    out[0] = INT_TO_HEX_CHAR((value >> 8) & 0x0F);
    out[1] = INT_TO_HEX_CHAR((value >> 4) & 0x0F);
    out[2] = INT_TO_HEX_CHAR(value & 0x0F);
    out[3] = '\0';
}

void adc_init() {
    ADMUX = (1 << REFS0); // AVcc reference, ADC0
    ADCSRA = (1 << ADEN)  // Enable ADC
           | (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0); // Prescaler = 128
}

uint16_t adc_read(uint8_t channel) {
    ADMUX = (ADMUX & 0xF0) | (channel & 0x0F);  // Select ADC channel
    ADCSRA |= (1 << ADSC);                     // Start conversion
    while (ADCSRA & (1 << ADSC));              // Wait for completion
    return ADC;
}

// description
int main() {
    char buffer[4];
	SREG |= ENABLE_GLOBAL_INTERRUPT;												// 7.3.1 : Status Register, bit 7 : I – Global Interrupt Enable
	uart_init();

	adc_init();

	while(1) {
        uint16_t value = adc_read(0); // Read from ADC0 (A0)
        // snprintf(buffer, sizeof(buffer), "ADC: %u\r\n", value);
		word_to_hex(value, buffer);
        uart_printstr(buffer);
        uart_printstr("\r\n");
        _delay_ms(20); // Wait 20ms
	}
}

// ISR(ADC_vect) {		// Table 12-6 : interrupt vector for ADC Conversion Complete
// }